Method For Manufacturing A Toothed Disc and The Toothed Disc Manufactured Thereby

ABSTRACT

A novel method of manufacturing a toothed disc is taught wherein the teeth can be cold formed to a relatively high set of tolerances in a relatively time-efficient manner. A cold-formed disc blank with an annular thickened ring about its periphery is forced through a set of tooth forming rollers which engage the annular thickened ring. As the blank is forced through the set of rollers, the rollers cold forming tooth structures in the annular ring. In some circumstances, the tooth structure can be a final desired tooth profile and in other circumstances, the disc blank may be forced through two or more different sets of tooth forming rollers, each set of tooth forming rollers contributing to the forming of the final, desired tooth profile.

FIELD OF THE INVENTION

The present invention relates to a method of manufacturing a tootheddisc and the toothed disc produced by the method. More specifically, thepresent invention relates to a method of cold forming a disc with a setof radially extending gear teeth about the periphery of the disc and thedisc formed thereby.

BACKGROUND OF THE INVENTION

It is well known to form a toothed disc by cold forming the disc from asteel blank and then forming the desired teeth thereon. Such discs canbe used for a variety of purposes, such as flex plates for internalcombustion engines, etc. In the specific case of flex plates, the teethformed on the periphery of the disc are engaged by the engine's startermotor to rotate the crankshaft of the engine to start the engine.

For example, U.S. Pat. Nos. 5,152,061; 5,203,223; 5,237,744; and5,404,640 to Himmeroeder, which are assigned to the assignee of thepresent invention and the contents of each of which patents areincorporated by reference herein, disclose methods of cold forming atoothed disc from a steel blank. In the first three Himmeroeder patentsmentioned above, an annular thickened ring is cold formed about theperiphery of the disc and a tooth forming device, in the form of a gear,engages this thickened ring and is synchronously rotated about theperiphery of the disc to press-form the desired teeth into the thickenedring to finish the disc.

While the methods taught in the first three above-mentioned patents toHimmeroeder have been commercially successful, when the teeth are formedsolely by cold press forming, it has proven difficult to achieve tighttolerances in the shape of the teeth. In U.S. Pat. No. 5,404,640,Himmeroeder discloses that to achieve tighter tolerances, the forming ofthe teeth can be completed with a hobbing operation which removesundesired material accumulated in the teeth during the coldpress-forming operations.

Further, the need in the Himmeroeder methods to rotate the cold formeddisc with a tooth forming device and, in some cases, to performsubsequently hobbing on the teeth requires a significant amount of timeto complete the manufacture of the disc and incurs a correspondingmanufacturing expense.

U.S. Pat. No. 5,878,493, also to Himmeroeder and assigned to theassignee of the present invention and the contents of which are alsoincorporated by reference herein, discloses a method of cold forming adisc with an annular thickened ring and then forming the desired teethabout the thickened ring by indexed rotation of the disc and a hobbingoperation to completely form each tooth. While the disclosed methodprovides for the formation of the teeth with very tight tolerances, themanufacturing time required to form each tooth by hobbing issignificant, again resulting in a relatively high manufacturing cost.

It is desired to have a method of manufacturing a toothed disc whichallows for tight tolerances on the formation of the teeth while alsoreducing the cost and/or time of manufacture.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a novel method ofmanufacturing a toothed disc, and the toothed disc produced from themethod, which obviates or mitigates at least one disadvantage of theprior art.

According to a first aspect of the present invention, there is provideda method of cold forming a toothed disc, comprising the steps of:stamping a disc blank from a feedstock; cold forming an annularthickened ring about the periphery of the disc blank; and forcing thedisc blank through a set of tooth forming rollers which engage theannular thickened ring to cold form a set of tooth structures about theannular thickened ring.

The present invention provides a novel method of manufacturing a tootheddisc wherein the teeth can be cold formed to a relatively high set oftolerances in a relatively time-efficient manner. A cold-formed discblank with an annular thickened ring about its periphery is forcedthrough a set of tooth forming rollers which engage the annularthickened ring. As the blank is forced through the set of rollers, therollers cold-forming tooth structures in the annular ring. In somecircumstances, the tooth structure can be a final desired tooth profileand in other circumstances, the disc blank may be forced through two ormore different sets of tooth forming rollers, each set of tooth formingrollers contributing to the forming of the final, desired tooth profile.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will now be described, byway of example only, with reference to the attached Figures, wherein:

FIG. 1 shows a cross section through a portion of a cold-formed discblank used in the present invention;

FIG. 2 shows a cross section of the portion of the disc blank of FIG. 1being moved past a tooth-forming roller in accordance with the presentinvention;

FIG. 3 a top view of a portion of the disc blank of FIG. 2 being movedpast a set of tooth forming rollers; and

FIG. 4 shows a schematic representation of a multi-stage press which canbe employed with the method of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A method of manufacturing a toothed disc, in accordance with the presentinvention, commences with the forming of a suitable disc blank with anannular thickened ring upon which the desired teeth can subsequently beformed. Any suitable method of forming the disc blank can be employed,such as the cold forming methods illustrated in the above-mentionedpatents to Himmeroeder or by any other suitable method, as will occur tothose of skill in the art.

Once a suitable disc blank has been formed, the method continues with atleast one, and preferably two or more, tooth forming operations beingperformed on the thickened annular ring of the disc blank.

Specifically, as shown in FIG. 1, a tooth forming operation commenceswith the web portion 20 of the disc blank being loaded into held atwo-part carrier 24 a, 24 b that abuts the upper and lower surfaces ofweb portion 20 inside the thickened annular ring 28 of the disc blank,exposing the annular ring.

The formed disc blank in carrier 24 is then moved through a set of toothforming rollers 32 which engage the outer periphery of thickened annularring 28 and cold form radially extending teeth therein. In the firstpreferred embodiment, the number of rollers 32 corresponds to the numberof desired teeth to be formed in the final toothed disc. Each roller hasan axis of rotation that is radially tangential to the axial directionas indicated by arrow 38. In other words, the axis of rotation of eachof the rollers 32 is preferably orthogonal to the axis of rotation ofthe disc blank. As shown in FIG. 2, the disc blank (the carrier has beenomitted from this Figure for clarity) is first in an initial position,indicated at 36, wherein thickened annular ring 28 does not contacttooth-forming roller 32.

Next, the disc blank and the carrier 24 is driven to move axially frominitial position 36, in the direction indicated by arrow 38, in thedirection of the axis of rotation of the disc blank, throughintermediate positions indicated at 40, 44, and 48, wherein eachtooth-forming roller 32 traverses thickened annular ring 28 to cold formsimultaneously a series of teeth in thickened annular ring 28.

The tooth forming operation completes when the disc blank reaches afinal position, indicated at 52, wherein thickened annular ring 28 hascompletely traversed each tooth forming roller 32 and teeth, of depth56, have been formed in ring 28 simultaneously by each tooth formingroller 32.

A separate tooth-forming roller 32 is used to form each tooth on annularring 28. FIG. 3 shows one arrangement of tooth forming rollers 32 aboutthe periphery of the disc.

As will be apparent to those of skill in the art, depending upon thedesired shape, depth and/or spacing of the teeth to be formed in annularring 28, it may be required or preferred to form the final teeth in twoor more tooth forming operations. For example, if the teeth to be formedare relatively closely spaced, it may be difficult to arrangetooth-forming rollers 32 in the desired/required spacing about theperiphery of the disc. In such a case, it is contemplated that anarrangement can be employed of tooth forming rollers 32 to form everysecond tooth and a first tooth forming operation can be performed toform a first half number of the desired teeth, after which a secondtooth forming operation can be performed to form the remaining half ofthe desired teeth. This second tooth forming operation can be performedby, for example, rotating the disc and carrier 24 by one tooth-widthafter the first tooth forming operation has completed and again movingthe disc blank through the set of tooth forming rollers 32 to form themissing teeth. Alternatively, the disc blank with one half or thedesired teeth can be moved to a second forming station wherein the discblank is loaded into a second carrier 24, in an indexed manner to assureits rotational orientation, and then the disc blank can be moved througha second set of tooth forming rollers 32 which are positioned to formthe missing teeth.

It is also contemplated that, depending upon the properties of thematerial from which the disc is formed, and the desired depth of theteeth and the desired shape of the teeth, it may be difficult orimpractical to form the teeth with a single tooth forming operation. Insuch a case, the first tooth forming operation may employ a set of toothforming rollers 32 with a profile that is suitable for a first formingoperation and a second tooth forming operation can be performed with aset of tooth forming rollers 32 which have the desired final profile,the second set of tooth forming rollers being moved through, andfinishing, the structures formed in annular ring 28 by the first set oftooth forming rollers 32.

It is contemplated that the first and second tooth forming operationscan be performed in any suitable manner, such as at two separate formingstations, with the disc blank being appropriately indexed to assurealignment of the second set of tooth forming rollers 32 with thepreliminary structures formed by the first set of tooth forming rollers32, or at a single forming station wherein the disc blank is movedthrough both the first set of tooth forming rollers 32 and then throughthe second set of tooth forming rollers 32 to complete the formation ofthe teeth.

If required, or desired, three or more tooth forming operations can beperformed, either forming the final tooth profiles in incremental stepswith sets of tooth forming rollers 32 having different profiles, orforming subsets of the total number of teeth to permit the location andarrangement of tooth forming rollers 32 about the periphery of the discblank or in a combination of both types of operation.

If desired, once the final tooth forming operation has been performedand the formed teeth have the desired profile, the teeth can hardened byheat treating, or any other suitable hardening process as will occur tothose of skill in the art. However, it is contemplated that, in manycircumstances, no further treatment will be required once the finalprofile has been formed.

FIG. 4 shows a schematic representation of a multi-station press 100which can be used to implement the method of the present invention.Specifically, a coil 104 of steel is supplied to a feeder 108 whichsupplies a suitable feed of steel feedstock 112 to the first station 116of press 100 wherein a disc blank is stamped from the steel feedstock112 during one cycle of press 100. This stamping operation can form thecircular disc, as well as remove undesired material from the center areaof the disc and any weight saving areas.

As press 100 opens during the next cycle, the disc blank is moved to thesecond station 120 which can perform one or more of the steps requiredto cold form the thickened annular ring 28 of the disc. As press 100opens during the next cycle, the disc blank is moved to the thirdstation 124 which performs one or more steps required to complete thecold forming of the disc blank with the thickened annular ring 28.

As press 100 opens during the next cycle, the finished disc blank ismoved to the fourth station 128 wherein a first tooth forming process isperformed with a first set of tooth forming rollers.

Again, as press 100 opens during the next cycle, the disc blank with thepartially formed set of teeth is moved to the fifth station 132 whereina second tooth forming process is performed with a second set of toothforming rollers. As press 100 opens during the next cycle, the nowfinished toothed disc is removed from press 100 and can be furthertreated, if desired, to harden the finished teeth, etc.

In the illustrated embodiment, each of the two tooth forming processesare performed at a separate station, in this case stations 128 and 132.However, as is also mentioned above, it is also contemplated that, insome circumstances, more than one set of tooth forming rollers 32 can beprovided at a single station. For example, if station 128 is equippedwith two sets of tooth forming rollers 32 which are spaced apart (in thedirection of the stroke of press 100) from one another. In such a case,as press 100 cycles the disc blank is then forced through first one setof tooth forming rollers 32 and then through the second set of toothforming rollers 32. It is contemplated that, in at least somecircumstances, depending upon the useful stroke length of press 100, twoor more tooth forming operations can be performed in this manner at asingle station.

As will be apparent to those of skill in the art, it is expected thatthe toothed discs produced with the method of the present invention canbe produced in a continuous fashion, with disc blanks beingappropriately processed simultaneously at each station of press 100before being moved to the next station or being completed. As will alsobe apparent to those of skill in the art, the present invention is notlimited to use with a five-station press and fewer or more stations canbe employed as necessary, depending upon the design of, and requirementsfor, the finished toothed disc. Nor is the present invention limited tothe use of a multi-station press and separate devices and/or machinescan be employed for one or more of the stages of the process if desired.

It is also contemplated that additional manufacturing operations can beperformed at appropriate points during the manufacturing process. Forexample, the disc blank can be heat treated to harden it once annularthickened ring 28 has been formed. Or, thickened annular ring 28 can beheat treated before the disc blank is forced through tooth formingrollers 32, or after being forced through one set of tooth formingrollers 32 and before being forced through the next set of tooth formingrollers 32, etc. It is also contemplated that the disc blank can besubjected to piercing operations to remove undesired material and/or toother machining operations to form threaded bores, etc., as desired.

Depending upon the required strength for the formed toothed disc, it ispresently contemplated that a work hardening steel, such as TRIP steel,may be preferred as the feedstock material. It is further contemplatedthat the temperature of the work hardening steel can be raised, duringthe manufacturing processes, as needed to permit the forming of theteeth with tooth forming rollers 32.

The present invention provides a novel method of manufacturing a tootheddisc wherein the teeth can be cold formed to a relatively high set oftolerances in a relatively time-efficient manner. A cold-formed discblank with an annular thickened ring about its periphery is forcedthrough a set of tooth forming rollers which engage the annularthickened ring. As the blank is forced through the set of rollers, therollers cold forming tooth structures in the annular ring. In somecircumstances, the tooth structure can be a final desired tooth profileand in other circumstances, the disc blank may be forced through two ormore different sets of tooth forming rollers, each set of tooth formingrollers contributing to the forming of the final, desired tooth profile.

The above-described embodiments of the invention are intended to beexamples of the present invention and alterations and modifications maybe effected thereto, by those of skill in the art, without departingfrom the scope of the invention which is defined solely by the claimsappended hereto.

1. A method of cold forming a toothed disc, comprising the steps of:providing a disc blank having an annular ring about a periphery of thedisc blank; and forcing the disc blank through a set of tooth formingrollers which engage the annular ring to cold form simultaneously aseries of tooth structures in the annular ring.
 2. The method of claim 1wherein the tooth forming rollers each has a tooth forming profilecorresponding to a desired tooth profile and the tooth structures coldformed in the annular ring are the desired tooth profile.
 3. The methodof claim 1 wherein the tooth forming rollers each has a tooth formingprofile corresponding to a first tooth profile and the tooth structurescold formed in the annular ring are a first tooth profile and the methodfurther comprising the step of forcing the disc blank through a secondset of tooth forming rollers which engage the set of tooth structures tomodify the set of tooth structures to a second tooth profile.
 4. Themethod of claim 3 wherein the second tooth profile is the desired toothprofile.
 5. The method of claim 3 wherein the disc blank is forcedthrough a third set of tooth forming rollers which engage the set oftooth structures to modify the set of tooth structures to a third toothprofile.
 6. The method of claim 5 wherein the third tooth profile is thedesired tooth profile.
 7. The method of claim 1 wherein the series oftooth structures formed is a subset of the total number of teeth to beformed in the annular ring, the method further comprising the subsequentstep of forcing the disc through a second set of tooth forming rollersto cold form a second set of tooth structures about the annular ring,each tooth structure of the second set of tooth structures being locatedbetween adjacent ones of the previously formed set of tooth structuresto form the total number of teeth desired in the annular ring.
 8. Themethod of claim 1 wherein the series of tooth structures formed is asubset of the total number of teeth to be formed in the annular ring,the method further comprising the subsequent step of rotating the discblank a selected amount before forcing the disc blank through the set oftooth forming rollers a second time to form a second series of toothstructures.
 9. The method according to claim 8 wherein said set of toothforming structures have an axis of rotation orthogonal to an axis ofrotation of the disc blank.
 10. The method of claim 9 wherein said discblank is forced in an axial direction relative to the axis of rotationof the disc blank.
 11. The method according to claim 10 wherein saidstep of forcing includes loading the disc blank in a two-part carrierthat abuts the upper and lower surfaces of the disc blank and exposesthe annular ring, said carrier configured to move in a directionorthogonal to the axis of rotation of each rollers of the set of toothforming rollers.